Apparatus for nitric acid purification



G. H. TOZIEE.

APPARATUS FOR NITRIOACID PURIFICATION.

' APPLICATION map MAY 24. 1921.

1,429,177.. Pt'entedSept. 12,1922.

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WITNESS 1 INVENTOR ATTORNEY 40 cost of distillation.

Patented Sept. 12, 1922.

UNITED STATES. PATENT OFFICE.

GEORGE E. TOZIER, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COM- PANY, OF NEW YORK, A CORPORATION OF NEW YORK.

APPARATUS FOR NITRIC ACID PURIFICATION.-

Appl ication filed May 24,

To all whom an may concern Be it"known that I, GEORGE H. Tozmn, a citizen of the United States of America, residing at Rochester, in the county of 6 Monroe and State of New York, have invented certain new and useful Im rovements in Apparatus for Nitric Acid urification, of which the following is a full, clear, and exact specification.

This invention relates to the concentration and purification of nitric acid. One object of the invention is to provide an apparatus by which nitric acid may be concentrated rapidly and relatively inexpensively, while at the same time it is substantially freed from metallic impurities, particularly .iron compounds. Another object of my invention is to provide a comparatively cheap apparatus which will readily concentrate and urify nitric acid, so as to substantially free it from metallic salts, especially those of iron, even when parts of the apparatus are composed of iron alloys. Further objects will hereinafter appear.

In the accompanying drawing, the single figure is a diagrammatic side elevation of an apparatus embodying my invention.

For certain purposes, such as in the manufacture of photographic materials for in- 8 stance, it'i'slhighly desirable to obtain con-- ,oentrated nitric acid substantially free from iron, the latter, if present at all, appearlng as the 'merest trace. Now if the purifying -ap-' paratus, in order to avoid contamination, be

.85 all composed of non-ferrous material, like lass, it is necessarily limited as to size, is ragile, and relatively expensive; while the 'use of a platinum still requires a very lar e investment and thus greatly increases t e 7 Certain iron alloys while strong and relatively inexpensive and considerably resistant tohotnitric acid are, neverth less, slightly attacked by the latter,

' so that tne body of acid in a still of this mate- 4lijrial becomes contaminated with iron compounds during distillation. These compounds tend' to pass over into the condenser so as to be present in undesirable quantities in the final roduct. This is especially true where the distillation is conducted rapidly enough for commercial purposes.

The problem has, therefore, been to utilize the strong, inexpensive and fairly resistant ironalloys in the purifying apparatus,

56 while at the same'obtaining a product sub- 1921. Serial No. 472,247.

stantailly free from iron. have discovered that the iron compounds are carried from the still to the condenser in minute particles of acid, which are mechanically conveyed by the stream of vapor. I have found that this 60 can be prevented without injuriously slowing down the distillation, by placing a partially refluxing condenser between the still and the ultimate condenser, the latter then acting in a complementary capacity to the partially refluxing condenser. In the latter, part of the vapor is condensed and drops backward into the still, during such movement sweeping back into the still the aforementioned small particles'of contaminated acid and thus preventing their movement over into the final condenser.

Referring now to the drawing, which illustrates diagrammatically merely one of the many forms in which my invention may be embodied, 1 is the still which, in the referred form of my invention, is com os of a high silicon iron alloy, like urion which may contain approximately 14% of silicon. 2 is a steam jacket for heating the still, the steam entering the inlets 3 and passing out through the outlets. 5, 6 and 7 indicate respectlvely-the vent, draw-ofi,

and feed nozzle of the still, all of which parts are welLknown to those skilledin the distillation of nitric acid. All of the sev-' eral inlets and outlets to the still and steam jacket are provided with regulating valves, these being omitted from the drawing for the sake of clearness, they being also well known.

From the top of the still there extends upwardly a pipe 8 in which the partial condensation takes place. This pipe is made of a material that is substantially completely resistant to the nitric acid, whether in liquid or vapor form. 'I prefer to use a tube of siliceous material, such as a glass of relatively low co-efiicient of expansion, or fused quartz, which can thus resist sudden 100 changes of temperature. Pyrexglass may thus be employed.

The temperature of the reflux condenser is preferably kept sufliciently below the temperature of the still to condense just enough lob vapor to wash the contaminated particles back into the main body of acid. Of course, larger amounts of vapor can be, condensed in the refluxing apparatus, but any considerable excess of condensation above the 110 amount needed to, safely wash down the contaminated particles represents a neegl cated in the drawing) in a jacket 9 provided with an inlet 10 and outlet 11. Hot water or steam may be circulated through-this jacket at a temperature that is sufliciently less than that in the still 1. Thus if the steam in jacket 2 is at 24 pounds pressure (which may be usefully employed, for example, when distilling 60% nitric acid) that in the jacket 9 may be at a considerably reduced pressure. The operator has merely to lower the temperature in jacket 9 until' the acid in the final condenser is found to be After the dif-.

sufiiciently free from iron. ference in temperature between jackets 2 and 9 is thus established, it can be readily maintained.

Instead of using a jacket 9, the pipe 8 may be made sufliciently long to be air cooled, the rate of coolin being controlled by a thin heat retarding coating. The longer the pipe 9 the thinner will be this retarding coating. It may be initially adjusted by thinning do .1 a too thick coating until the iron compounds fail toappear in harmful amounts in the final acid, If air cooled, the pipe 8 may be made of thin walled Pyrex glass, say 6 or 7 feet in length, and lightly coated with a magnesia compound.

The residual vapors, washed free from particles-containing iron compounds, then pass through connection 11' to an ultimate condenser 12 which is more or less conventionally represented as being composed of a zigzag series of ipes 13 supported by columns 21 and coo ed by water or spray falling from the pipe 14 controlled by valve '15. The columns 21 may rise from a base 22 carried on any suitable foundation or support 23. The coils or pipes 13 are composed of material that is substantially completely resistant to nitric acid, siliceous material like glass being noted as particularly useful. Glass of low co-efficient of expansion, like Pyrex, is preferable, but not indispensable.

The pure concentrated acid'flows from the complementary condenser 12 through connection 16 to the series of containers 17, the latter being connected by pipes 18. These containers are located upon any suitable foundation or support 24:, the latter being preferably below the level of the condenser outlet so as to permit of a proper flow of acid by gravity. In these containers air, warmed if necessary, is blown through the acid frompipes 19 to remove nitrogen oxides and any chlorine, bromine or other gaseous impurities, 20 being a series of vents. The acid then flows through the trap 21 into a.

a l-ear??? storage vessel or shipping container, as will be readily understood. i I

While I have illustrated certainemhodiments of my invention, it is to be understood that the structure of the apparatus may be considerably varied "and the method of distillation may be variously altered without departing from the principle of my invention as defined in the following claims.

Having thus described my invention, what 1 claim as new and desire to secure by Letters Patent is:

. 1. Apparatus for obtainingconcentrated and purified nitric acid, comprising a still, a partially refluxing condenser substantially completely resistant to saidconcentrated acid, and a complementary condenser connected in series.

2. Apparatus for preparing highly concentrated and purified nitric acid, comprising a still, the acid-contacting material oi which is slightly attacked by nitric acid, a partially refluxing condenser connected to said still and a complementary condenser connected with said refluxin condenser, the acid-contacting materials 0 both of said condensers .being substantially completely resistant to said acid.

3. Apparatus for preparing concentrated nitric acid substantially free from iron com pounds, comprising a still of iron alloy which is slightly attacked by nitric acid, a partially refluxing condenser connected to said still and a complementary condenser connected with said refluxing condenser, the acid-contacting materials of both said condensers being substantially completely resistant to said acidf 4:. Apparatus for obtaining highly concentrated nitric acid substantially free from iron compounds, comprising a still of silicon iron alloy which is slightly attacked by nitric acid, a partially refluxing condenser connected to said still, a complementary condenser connected to said refluxing condenser, the acid-contacting materials of both said containers being substantially completely resistant to said acid.

5. Apparatus for obtaining highly concentrated nitric acid substantially free from condensers which contact with the Vapors and acid being composed of siliceous material.

7. Apparatus for preparing concentrated and purified nitric acid, comprising a still which slightly contaminates the nitric acid contained therein, a partially refluxing condenser connected to said still, the acid-contacting surfaces of which are composed of siliceous material of low co-efiicient of expansion and a complementary condenser connected to said refluxing condenser, and being substantially completely resistant to nitric acid.

8. Apparatus for preparing concentrated nitric acid substantially free from iron compounds, comprising a still of iron alloy,

which is slightly attacked by nitric acid, a partially refluxing condenser connected to said still and a complementary condenser connected with said refluxing condenser, the

acid-contacting surfaces of both said condensers being composed of siliceous material.

9. Apparatus for preparing concentrated nitric acid substantially free from iron compounds, comprising a still of silicon iron alloy which is slightly attacked by nitric acid, a partially refluxing condenser connected to said still, and a complementary condenser connected with said refluxing con denser, the acid-contacting faces of both said 7 silicon, a partially refluxing condenser above and connected to said still, the acid-contacting material of said condenser being glass of low co-efiicient of expansion, a complementary condenser connected to said refluxing condenser and having its acid-contacting surfaces com osed of glass.

Signed at day of May 1921;

- GEORGE TOZIER.

ochester, New York, this 9th ree from 

